The present invention relates to a steering linkage for vehicles, and, more particularly, to a steering linkage for vehicles of the type having rigid axles.
A steering linkage for rigid axle vehicles generally comprises left and right side knuckle arms, a tie rod which pivotably connects said knucle arms with each other, a Pitman arm, and a relay rod which pivotably connects said Pitman arm with said tie rod. In this case, the knucle arms and opposite ends of the tie rod are individually connected with each other by ball joints so that, when one or the two of the left and right side wheels related with the left and right side knucle arms move up and down during running of the vehicle, the knucle arms can pivot vertically around the pivot centers of the ball joint relative to the tie rod as well as other linkage elements substantially stationarily supported by the body of the vehicle. Further, in a conventional steering linkage of this type, the relay rod and the tie rod are also connected with each other by means of a ball joint which is mounted to one side of the tie rod by one of its two mutually pivotable members so that the pivot center of the ball joint is positioned at the same mounting level with the central axis of the tie rod which is generally a straight bar whose central axis is substantially in coincidence with a straight line which connects the pivot centers of the two ball joints connecting the knucle arms with opposite ends of the tie rod. On the other hand, the pivotable connection between the Pitman arm and the relay rod is generally positioned at a higher mounting level than the pivotable connection between the relay rod and the tie rod, and accordingly the relay rod is generally positioned so as to incline downwards from its one end connected with the Pitman arm towards its other end connected with the tie rod. In this case, since the axis of the relay rod does not pass the central axis or the rotary axis of the tie rod, when the relay rod is pushed towards or pulled apart from the tie rod in accordance with turning of the Pitman arm for the purpose of steering, the tie rod is first rotated around its central or rotary axis due to a moment produced by the pushing or pulling force exerted along the axis of the relay rod and the distance of discrepancy between the axes of the relay rod and of the tie rod before the tie rod is shifted in the steering direction along its axis. When this occurs, the initial steering function by rotation of the Pitman arm is cancelled, thereby interferring with normal feeling of the steering system.